The specific goals of the proposed research are: to detemine the content and composition of lipids in the undegraded mucus glycoprotein isolated from gastric mucus; to establish the requirements of glyceroglucolipids for for interacting with mucus glycoprotein, and to determine whether this interaction involves the protein or carbohydrate component of the glycoprotein; to provide the information as to the topography of lipids within the undegraded gastric mucus glycoprotein polymer; to determine whether glyceroglucolipids protect the mucus glycoprotein polymer from the degradation by pepsin; to determine the effect of lipids on the rheological properties of mucus glycoprotein, and J to evaluate the role of mucus lipids in the process of H+ retardation by gastric mucus; to determine whether activities of enzymes involved in the biosynthesis of glyceroglucolipids in gastric mucosa of patients with gastric diseases differ from that of normals. The undegraded mucus glycoproteins, isolated from pig, dog and rat gastric mucus by the equilibrium centrifugation in CsCl density gradient, will be used to study the content and composition of lipids. Dissociation of the undegraded mucus glycoproteins into a central protein component and the reduced glycoprotein monomers will be performed by the reductive cleavage of dissulfide bridges. The effect of lipids on the peptic digestion of mucus glycoprotein will be measured by the trinitrophenylation method. Viscosity measurements and the study on the role of lipids in the retardation of H+ diffusion by gastric mucus will be performed on the intact and delipidated mucus and glycoprotein. Human gastric mucosal biopsy specimens will be used to study the activities of enzymes involved in the biosynthesis of glyceroglucolipids.